588 FIFTH REPORT OF THE ENTOMOLOGICAL COMMISSION. 
founded, they may be distinguished by the following characters in addition to those 
of the family Tenthredinida* to which these insects belong: 
Tin* first, Dolerus arvtn>i«. ifl a little more than one-third of an inch in length by 
about one-third as wide, and measures not far from two-thirds of an inch across the 
extended wings. The head and body are dark steel blue except the thorax, which is 
gated with yellow and black. 
07. DoUruH bicolor Beany. 
Referring to the second species of Dolerus, Forbes continues bis 
account as follows \ 
The other species, Dolerus bicolor, is a trifle smaller than the lirst, brownish yellow 
except the wings, the head, the middle of the thorax, and the legs, all of which are 
black. 
Both these insects are abundant everywhere in early spring, and the larva' of both, 
similar in appearance to green caterpillars, but distinguished by the possession of 
eleven pairs of legs, feed upon the leaves of the willow a little later in the season. 
Careful watching in the held soon convinced me that these saw-flies were neither 
biting nor piercing the buds or flowers, but that they were merely licking off the 
semi-fluid exudation from the surface of the bud scales. Dissecting the specimens 
and examining the contents of their stomachs with the microscope, I found only a 
clear fluid, without a trace of solid matter except occasional spheres consisting of 
clusters of threads of fungous parasites Critically searching the surface of a bud 
scale which these flies had but just worked over, I saw that no injury whatever had 
been done to the tissues of the plant, even the slender hairs with which the scales 
were covered being wholly undisturbed. Watching the flies with a glass, I could 
see that their biting jaws remained all the time closed, but that their flap-like max- 
ilhe were continually employed in mopping up the moisture from the viscid surface, 
and as they have no mouth-parts capable of piercing the substance of a plant, it was 
clear that no injury was being done. Finally, I confined a lot of the saw-flies in a 
breeding cage with pear buds not yet open. The insects industriously worked over 
the surfaces of the unopened buds and even entered the flowers as they expanded, 
but did neither any visible injury whatever. The buds afterwards all opened out in 
abundant bloom, and remained fresh for several days, while the poor saw-flies, hav- 
ing lapped up all the sirup available, starved to death in the midst of the uninjured 
blossoms. A little experiment showed that they were especially susceptible to the 
influence of pyrethrum, and that a single thorough application to a tree would kill 
all upon it at the time. 
The above brief account of these insects is given merely to set at rest the fears of 
those who, like my correspondents, may be led to attribute to them serious mischief 
really due tc quite other causes. (Forbes.) 
68. Nematua ventralis Say. 
The larvae of tbis saw-fly were found by Dr. Harris on leaves of the 
willow June 22; they spun tbeir cocoons June 24, tbe flies appearing 
from July 15 onward. A second brood of these occurred on the nar- 
row-leafed dwarf willow September 5, and on the same shrub a pair 
of flies apparently recently transformed. The cocoons were made Sep- 
tember 20. A swarm of larvse was also found October 17. (Harris r 
Corr., p. 270.) 
Larva.— Six-tenths inch long, greenish black, and with ten heart-shaped ocher-yel- 
low spots on each side, beginning on the second ring. Prolegs fourteen ; viz, twelve 
ventral and two very short retractile ones to the last ring, all of a whitish color; 
the first nair on the fifth ring, and the rest (except the anal pair) on the following 
